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some constant propagation optimizations

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This commit is contained in:
Ulf Norell 2019-04-29 12:40:50 +02:00
parent 4c2288274d
commit 389a5c4e62
1 changed files with 103 additions and 14 deletions
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107
src/aeso_fcode_to_fate.erl
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@ -693,7 +693,15 @@ swap_instrs({i, #{ live_in := Live1 }, I}, {i, #{ live_in := Live2, live_out :=
{{i, #{ live_in => Live1, live_out => Live2_ }, J},
{i, #{ live_in => Live2_, live_out => Live3 }, I}}.
live_in(R, #{ live_in := LiveIn }) -> ordsets:is_element(R, LiveIn).
live_in(R, #{ live_in := LiveIn }) -> ordsets:is_element(R, LiveIn);
live_in(R, {i, Ann, _}) -> live_in(R, Ann);
live_in(R, [I = {i, _, _} | _]) -> live_in(R, I);
live_in(R, [switch_body | Code]) -> live_in(R, Code);
live_in(R, [{switch, A, _, Alts, Def} | _]) ->
R == A orelse lists:any(fun(Code) -> live_in(R, Code) end, [Def | Alts]);
live_in(_, missing) -> false;
live_in(_, []) -> false.
live_out(R, #{ live_out := LiveOut }) -> ordsets:is_element(R, LiveOut).
%% -- Optimizations --
@ -732,7 +740,8 @@ apply_rules_once([{RName, Rule} | Rules], I, Code) ->
merge_rules() ->
[?RULE(r_push_consume),
?RULE(r_one_shot_var),
?RULE(r_write_to_dead_var)
?RULE(r_write_to_dead_var),
?RULE(r_inline_switch_target)
].
rules() ->
@ -740,6 +749,8 @@ rules() ->
[?RULE(r_dup_to_push),
?RULE(r_swap_push),
?RULE(r_swap_write),
?RULE(r_constant_propagation),
?RULE(r_prune_impossible_branches),
?RULE(r_inline_store)
].
@ -812,10 +823,75 @@ r_swap_write(Pre, I, Code0 = [J | Code]) ->
end;
r_swap_write(_, _, _) -> false.
%% Precompute instructions with known values
r_constant_propagation({i, Ann, I}, Code) ->
case op_view(I) of
false -> false;
{Op, R, As} ->
Vs = [V || ?i(V) <- As],
case length(Vs) == length(As) of
false -> false;
true ->
case eval_op(Op, Vs) of
no_eval -> false;
V -> {[{i, Ann, {'STORE', R, ?i(V)}}], Code}
end
end
end;
r_constant_propagation(_, _) -> false.
eval_op('EQ', [X, Y]) -> X =:= Y; %% TODO: more
eval_op(_, _) -> no_eval.
%% Prune impossible branches from switches
r_prune_impossible_branches({switch, ?i(V), Type, Alts, missing}, Code) ->
case pick_branch(Type, V, Alts) of
false -> false;
Alt -> {Alt, Code}
end;
r_prune_impossible_branches({switch, ?i(V), boolean, [False, True] = Alts, Def}, Code) ->
Alts1 = [if V -> missing; true -> False end,
if V -> True; true -> missing end],
case Alts == Alts1 of
true -> false;
false ->
{[{switch, ?i(V), boolean, Alts1, Def}], Code}
end;
r_prune_impossible_branches(_, _) -> false.
pick_branch(boolean, V, [False, True]) ->
Alt = if V -> True; true -> False end,
case Alt of
missing -> false;
_ -> Alt
end;
pick_branch(_Type, _V, _Alts) ->
false.
%% STORE R A, SWITCH R --> SWITCH A
r_inline_switch_target(Store = {i, _, {'STORE', R, A}}, [{switch, R, Type, Alts, Def} | Code]) ->
Switch = {switch, A, Type, Alts, Def},
case R of
?a -> {[Switch], Code};
{var, _} ->
case lists:any(fun(Alt) -> live_in(R, Alt) end, [Def | Alts]) of
false -> {[Switch], Code};
true -> {[Store, Switch], Code}
end;
_ -> false %% impossible
end;
r_inline_switch_target(_, _) -> false.
%% Inline stores
r_inline_store(I = {i, _, {'STORE', R = {var, _}, A = {arg, _}}}, Code) ->
r_inline_store(I = {i, _, {'STORE', R = {var, _}, A}}, Code) ->
%% Not when A is var unless updating the annotations properly.
r_inline_store([I], R, A, Code);
Inline = case A of
{arg, _} -> true;
?i(_) -> true;
_ -> false
end,
if Inline -> r_inline_store([I], R, A, Code);
true -> false end;
r_inline_store(_, _) -> false.
r_inline_store(Acc, R, A, [switch_body | Code]) ->
@ -987,7 +1063,12 @@ block(Blk = #blk{code = [{switch, Arg, Type, Alts, Default} | Code],
missing -> [{jump, DefRef}];
_ -> FalseCode ++ [{jump, RestRef}]
end,
{Blk#blk{code = ElseCode}, [{jumpif, Arg, ThenRef}], ThenBlk};
case lists:usort(Alts) == [missing] of
true ->
{Blk#blk{code = [{jump, DefRef}]}, [], []};
false ->
{Blk#blk{code = ElseCode}, [{jumpif, Arg, ThenRef}], ThenBlk}
end;
tuple ->
[TCode] = Alts,
{Blk#blk{code = TCode ++ [{jump, RestRef}]}, [], []};
@ -1018,7 +1099,7 @@ optimize_blocks(Blocks) ->
RBlocks1 = reorder_blocks(RBlocks, []),
RBlocks2 = [ {Ref, inline_block(RBlockMap, Ref, Code)} || {Ref, Code} <- RBlocks1 ],
RBlocks3 = remove_dead_blocks(RBlocks2),
RBlocks4 = [ {Ref, use_returnr(Code)} || {Ref, Code} <- RBlocks3 ],
RBlocks4 = [ {Ref, tweak_returns(Code)} || {Ref, Code} <- RBlocks3 ],
Rev(RBlocks4).
%% Choose the next block based on the final jump.
@ -1032,6 +1113,8 @@ reorder_blocks(Ref, Code, Blocks, Acc) ->
case Code of
['RETURN'|_] -> reorder_blocks(Blocks, Acc1);
[{'RETURNR', _}|_] -> reorder_blocks(Blocks, Acc1);
[{'CALL_T', _}|_] -> reorder_blocks(Blocks, Acc1);
[{'CALL_TR', _, _}|_] -> reorder_blocks(Blocks, Acc1);
[{'ABORT', _}|_] -> reorder_blocks(Blocks, Acc1);
[{switch, _, _}|_] -> reorder_blocks(Blocks, Acc1);
[{jump, L}|_] ->
@ -1069,10 +1152,16 @@ chase_labels([L | Ls], Map, Live) ->
New = lists:flatmap(Jump, Code),
chase_labels(New ++ Ls, Map, Live#{ L => true }).
%% Replace PUSH, RETURN by RETURNR
use_returnr(['RETURN', {'PUSH', A} | Code]) ->
%% Replace PUSH, RETURN by RETURNR, drop returns after tail calls.
tweak_returns(['RETURN', {'PUSH', A} | Code]) ->
[{'RETURNR', A} | Code];
use_returnr(Code) -> Code.
%% tweak_returns(['RETURN', {'PUSH', A} | Code]) ->
%% [{'RETURNR', A} | Code];
tweak_returns(['RETURN' | Code = [{'CALL_T', _} | _]]) ->
Code;
tweak_returns(['RETURN' | Code = [{'CALL_TR', _, _} | _]]) ->
Code;
tweak_returns(Code) -> Code.
%% -- Split basic blocks at CALL instructions --
%% Calls can only return to a new basic block.